Method and apparatus for ultrasonic testing of weld zones

Abstract

Provided are an ultrasonic testing method and an ultrasonic testing apparatus capable of accurately detecting flaws present in a weld zone of a test object, such as a welded pipe, regardless of the position of the flaws. An ultrasonic testing apparatus 100 includes an ultrasonic probe 1 which is provided with n (n≧2) transducers 11 arranged along a direction orthogonal to the weld line of a weld zone P1 of a test object P and is arranged so as to face the weld zone, and transmission / reception control means 2 which selects m (n>m≧1) transducers from the n transducers, causes the selected transducers to transmit and receive ultrasonic waves to and from the weld zone, and switches the selected transducers one after another. The transmission / reception control means switches the selected transducers one after another so that the range of an effective beam width of each of the selected transducers that have been switched for a flaw to be detected has an overlapping portion, and in the transmission / reception control means, the flaw detection sensitivity is adjusted beforehand for each of the selected transducers so that maximum echo intensities from a flaw to be detected, which are each received by each of the selected transducers that have been switched, become substantially equal to each other.

Description

TECHNICAL FIELD[0001]The present invention relates to an ultrasonic testing method and an ultrasonic testing apparatus capable of accurately detecting flaws present in a weld zone of a test object, such as a welded pipe or tube, regardless of the positions of the flaws. Hereinafter, “pipe or tube” is referred to as pipe when deemed appropriate.BACKGROUND ART[0002]Depending on welding methods and welding conditions, various flaws occur in a weld zone of a test object, such as a welded pipe. These flaws cause a quality deterioration of the weld zone. For this reason, the nondestructive inspection of weld zones is carried out using X-rays and ultrasonic waves.[0003]X-ray inspection can easily detect spot flaws, such as pinholes and slag inclusions, and has been used in many inspections. However, X-ray inspection has problems of low inspection efficiency, high equipment cost, and the like. For this reason, in submerged arc welded (SAW) steel pipe, ultrasonic testing is first performed a...

AI Technical Summary

Benefits of technology

[0028]The present invention was made in view of such problems with conventional techniques, and the object of the present invention is to provide an ultrasonic testing method and an ultrasonic testing apparatus which capable of accurately detecting flaws present in a weld zone of a test object, such as a welded pipe, regardless of the position of the flaws.

Problems solved by technology

Depending on welding methods and welding conditions, various flaws occur in a weld zone of a test object, such as a welded pipe.

These flaws cause a quality deterioration of the weld zone.

However, X-ray inspection has problems of low inspection efficiency, high equipment cost, and the like.

However, ultrasonic testing by ultrasonic probes of general K-form arrangement as shown in FIG. 1A has a problem as described below.

For transverse flaws, however, it is impossible to restrain the effects as described above because the ultrasonic testing of flaws on the inner and outer surfaces can be performed only in specific directions (the transfer direction of the steel pipe or the direction reverse to the transfer direction).

However, an increase in the number of ultrasonic probes to be arranged and the number of flaw detectors connected to each ultrasonic probe results in a steep rise in equipment cost.

In addition, because it is necessary to set the distance between a weld zone and an ultrasonic probe, flaw detection sensitivity and the like for each ultrasonic probe, addition of ultrasonic probes poses a problem of long adjustment time, which is necessary until flaw detection becomes possible.

It is difficult to simultaneously adjust the positions and the like of a pair of ultrasonic probes.

For this reason, this technique has the problem that although it is possible to detect flaws present in the center of the bead width direction, flaws present at positions away from the center of the bead width direction tend to be overlooked, and hence the practical application of the angle-beam ultrasonic testing using this above-bead probe has not easily moved ahead.

In other words, as illustrated as an example in FIG. 2, a bead (an excess weld metal) remains on the inner and outer surfaces of a weld zone and, therefore, it is difficult to simultaneously detect flaws present at positions different in the bead width direction of the weld zone.

However, it is difficult to detect the longitudinal hole A because of the low echo intensity.

As described above, after all, it is difficult for an ultrasonic probe provided with a single transducer to detect all flaws worked at different positions in the bead width direction.

However, the technique described in Patent Literature 2 has a problem as described below.

For this reason, in the practical effective beam width derived from a profile of sound field intensity, it is impossible to correctly determine the above-described switching pitch and flaws might be overlooked.

Images